1. Field
The present invention relates to a mobile communication terminal apparatus, particularly relates to a processing of reducing power consumed by a mobile communication terminal apparatus including two CPUs (Central Processing Unit).
2. Related Art
There is known a mobile communication terminal apparatus including two CPUs of a communication CPU used for operating a communication system and a user interface CPU used for user interface operation including display. It is known that the communication CPU is started when a communication operation is carried out, the user interface CPU is started when a dialogue operation with a user including display is carried out and when the respective operations have been finished, the respective CPUs reduce power consumption by low speed formation of a clock or the like.
Even when an apparatus is brought into a standby state, that is, a communication operation by an intention of the user is not carried out and the dialogue operation by the user is not carried out, it is necessary that the communication CPU carries out an intermittent receiving operation by being awakened intermittently. That is, it is necessary to investigate whether an incoming signal is transmitted from a base station to the apparatus. In the case of intermittent reception, the communication CPU is operated.
Further, even when the dialogue operation with the user is not carried out, there is a case in which the interface CPU informs that there is an incoming message which has not been called to the user by, for example, lighting LED by a predetermined period. Further, when predetermined time arrives, there is a case of informing the arrival of time. The user interface CPU is operated by the predetermined period or when the predetermined time arrives.
Here, it is particularly requested to reduce power consumed by two CPUs in the case of intermittent reception. Because a time period of bringing the apparatus into the standby state is long. Generally, useless power is consumed until CPU is started and is operated stably. Hence, it is known that power consumption can be reduced by reducing a number of times of starting CPU by making the CPU carry out other operation along therewith at time at which the CPU carries out an intermittent receiving operation (refer to JP-A-10-145285 (page 2, FIG. 2)).
However, according to the above-described method disclosed in JP-A-10-145285, it is not clear by what processing power consumption can be reduced in the apparatus having two CPUs.
On the other hand, a quality of a radio wave transmitted from the base station, for example, a strength of a signal to noise ratio is measured, a quality level of the radio wave is determined by comparing the measured quality of the radio wave with a predetermined threshold and the determined radio wave quality level is transmitted to a user interface CPU. In the intermittent reception, a communication CPU is operated.
Further, the user interface CPU displays an image in correspondence with a determined radio wave quality level at a pict column of a display portion. In order to carry out the display, the user interface CPU is operated.
Here, a power consumed by two CPUs in the intermittent reception is particularly requested to reduce. Because a time period of bringing the apparatus into a standby state is long. Hence, it is preferable that a number of times of transmitting operations from the communication CPU to the interface CPU is small, and there is known a processing of transmitting the determined radio wave quality level to the user interface CPU only when the determined radio wave quality level differs from a radio wave quality level determined in intermittent reception at a preceding time (refer to JP-A-2003-244316 (page 10, FIG. 2, FIG. 16)).
However, according to the method disclosed in JP-A-2003-244316, the quality of the radio wave is slightly changed at a vicinity of a predetermined threshold, as a result, a determined radio wave quality level is changed even when the radio wave quality is changed between upper and lower sides of the threshold. Therefore, a processing of transmitting the determined radio wave quality level to the user interface CPU is carried out frequently. Further, the interface CPU is operated to receive the determined radio wave quality level transmitted always from the communication CPU, and therefore, always power is consumed.